Lexus - Toyota OBD1 Diagnostic Trouble Code
21
Oxygen Sensor Signal
Area
Open or short in heater circuit of upstream oxygen sensor
Oxygen sensor heater
Engine Control Module(ECM)
Diagnosis
Open or short in heater circuit of heated oxygen sensor for 0.5 second or more. (HT)
At normal driving speed (below 60 mph and engine speed is above 1,500 rpm), amplitude of heated oxygen sensor signal (OX) is reduced to between 0.35 – 0.70 V continuously for 60 secs. or more.